Effect of region and dentin perfusion on bond strengths of resin-modified glass ionomer cements

Objectives: The purpose of this study was to evaluate the hypothesis that regional differences and pulpal pressure would significantly affect bond strengths of resin-modified glass ionomer cements to dentin. Methods: Twenty-six extracted caries-free human third molars were ground to expose middle dentin and were randomly divided into two groups for bonding: no pulpal pressure and pulpal pressure of 15 cm H₂O. Fuji II LC, Vitremer, or Photac-Fil Quick were applied to the previously pre-treated surfaces and light-cured as recommended by the manufacturers. After immersion in water at 37 °C for 24 h, the teeth were sectioned to 0.7 mm thick slabs, divided into pulp horn, center, and peripheral regions according to visual criteria, and trimmed along the bonded interface for microtensile bond test to a cross-sectional area of 1 mm². The slabs were subjected to tensile forces and the data analyzed using ANOVA and Fisher's PLSD at the 95% level of confidence. Results: For Fuji II LC, bond strengths to the pulp horn regions were significantly lower than those to the other regions independent of pulpal pressure (p < 0.05). On the other hand, regional bond strengths were not observed for Vitremer and Photac-fil Quick (p > 0.05). Conclusions: Pulpal pressure had a stronger influence on bond strengths and failure modes of resin-modified glass ionomers than regional differences of the substrate.